1. Field of the Invention
The present invention relates to a vehicle door latch device, and in particular, to a switch assembly that detects positions of a latch and a ratchet of the latch device.
2. Description of the Related Art
FIG. 7 illustrates a front face of a conventionally well known vehicle door latch device (latch unit), and onto a latch body A of the latch device, the latch body A being formed of a synthetic resin or the like, a latch C is pivotally supported by a latch shaft B and a ratchet E is pivotally supported by a ratchet shaft D. When a door moves to be closed, a striker F fixed to the body of the vehicle relatively advances into an advancement passage G formed in the latch body A, engages with an engagement groove H of the latch C, and rotates the latch C at an unlatched position in a full latch direction (clockwise direction). When the latch C is brought to a half latch position, the ratchet E is rotated by a spring elastic force in the clockwise direction and becomes engageable with a half latch engagement portion J of the latch C; when the latch C comes to a full latch position, the ratchet E becomes engageable with a full latch engagement portion K of the latch C; and when the ratchet E engages with the full latch engagement portion K of the latch C, the door closure operation is complete and the door is maintained in a closed state.
Further, a conventional latch unit is sometimes provided with an automatic closer function for rotating the latch C at the half latch position towards the full latch position by a motor power and an automatic releasing function for rotating a ratchet E by a motor power in a door opening direction (anticlockwise direction in FIG. 7) to separate the ratchet E from the full latch engagement portion K of the latch C and bring the door into an openable state (see, for example, Japanese Patent Application Laid-open No. 2014-009477). In this case, the latch unit is provided with a latch switch L that detects a position of the latch C and a ratchet switch M that detects a position of the ratchet E, and the automatic closer function and the automatic releasing function are controlled by signals from these switches being used.
In the latch unit illustrated in FIG. 7, the latch C (latch shaft B) and the ratchet E (ratchet shaft D) are respectively arranged separately, on a rear face side of the latch body A, to an upper side (latch side) and to a lower side (ratchet side) in the figure, of the advancement passage G of the striker (striker moving trajectory). With such an arrangement relation, an external force added from the striker F to the latch C is dispersed between and supported by the two shafts B and D above and below. In the industry, this arrangement structure is called “reaction force halving structure”, and this “reaction force halving structure” is the mainstream of the arrangement relation between a latch and a ratchet.
In a latch unit employing the “reaction force halving structure”, the latch switch L and the ratchet switch M are also respectively arranged separately to the latch side and the ratchet side divided by the advancement passage G, on the rear face side of the latch body A. Accordingly, two switch assemblies thus needing to be separately prepared and more than one step being required in the installation operation have been cost increasing factors.